Conventional safety switched outlets with dead fronts include a mechanical linkage interlocking the electrical receptacle and the switch. The linkage provided prevents the switch handle from being moved to an on position unless a plug is fully inserted in the electrical receptacle. Because the mechanical linkage prevents movement of the switch handle to the on position when no plug is in the receptacle, excessive force used in attempting to move the handle can break or bend the mechanical linkage, thereby damaging the outlet mechanism.
The disadvantage of these conventional mechanically interlocked systems is that users attempt to force movement of the handle to the on position, risking damaging the outlet mechanism. To avoid this problem, the outlet mechanism and components are usually made to be very strong to withstand the abuse. However, increasing the strength of the components is costly, makes the mechanism more difficult to operate, and is not always successful. Typical examples of conventional mechanically interlocked switched outlets which would cause linkage damage upon operation of the switch handle without a plug inserted in the receptacle are disclosed in U.S. Pat. No. 2,241,828 to Reynolds and U.S. Pat. No. 4,604,505 to Henninger.
U.S. Pat. No. 4,506,121 to Peterson discloses a mechanically interlocked switch outlet with a mechanism for preventing overloading of the switched linkage due to improper switch handle operation when a plug is not inserted in the receptacle. Such mechanism permits the handle to move from the off position to the on position without the plug being located within the electrical receptacle and without such handle movement actuating the switch or circuit breaker. In each of the several embodiments disclosed in the Peterson patent, a spring is provided in the mechanism which transmits force between the handle and the switch actuating mechanism. When the plug is inserted in the receptacle, the switch biasing force provides a force transmitting connection between the handle and the switch to actuate the switch. If no plug is received in the receptacle, the force transmission is impeded to an extent that will overcome the biasing force of the spring such that the handle moves to the on position without actuating the switch. However, the force override mechanism of the Peterson patent does not appear to be an effective solution to the problem of the conventional mechanically interlocked switched outlets.